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Nice one Cyril
…nice one son…let’s have another one!
😉I got the comet with a RedCat 51 last night. This has the same aperture as a Seestar 50 so it should be in range of those now although I had the advantage of a cooled camera and a dark sky at 2100 m on La Palma!
https://britastro.org/observations/observation.php?id=20250724_150857_253c99e511be2b41
The magnitude estimate on that image is probably rubbish since it is contaminated by stars but it is brighter than I expected.
I measure it as 17.0 with Astrometrica GAIA DR3 ‘g’ band filter.
https://britastro.org/observations/observation.php?id=20250726_151349_3fdc0db3f0b5c6df
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Hi all,
A better image from me. This time 36 x 90s with L filter.
https://britastro.org/observations/observation.php?id=20250728_122425_2b3fb6faab2f3379
I measured the V mag to be 17.5 +/-0.1 using an aperture radius of 12 pixels (0.48 “/pix) with APASS V mag band.
Ian
Ian,
It is worth submitting magnitude estimates to COBS if you can. There is a lot of scatter on the current estimates but they suggest that the comet might reach mag 14 in November as it comes out from solar conjunction.
Hi folks,
Newest image with the Baader 610 (R+IR) from the evening of the 4th August. Back on the 16″ scope, which helps. Half an hour and it looks bright, so it must have brightened appreciably since my last efforts.
NOrth is up in this, and it seems to show elongation to the right – is that correct? Seems like that would be towards the sun……
Hi Nick It seems that the coma elongation you have seen in your image is also recorded by HST, they comment that the extension is a plume ejected from the sunward side of the comet.
HST observed this comet and gave the following report.
Hubble’s observations are allowing astronomers to more accurately estimate the size of the comet’s solid icy nucleus. The upper limit on the diameter of the nucleus is 5.6 kilometers, though it could be as small as 320 metres across, researchers report. Though the Hubble images put tighter constraints on the nucleus size compared to previous ground-based estimates, the solid heart of the comet presently cannot be directly seen, even by Hubble. Observations from other observatories, including the NASA/ESA/CSA James Webb Space Telescope, will help refine our knowledge about the comet, including its chemical makeup.Hubble also captured a dust plume ejected from the Sun-warmed side of the comet, and the hint of a dust tail streaming away from the nucleus. Hubble’s data yields a dust-loss rate consistent with comets that are first detected around 480 million kilometres from the Sun. This behaviour is much like the signature of previously seen Sun-bound comets originating within our Solar System.
The big difference is that this interstellar visitor originated in some other Solar System elsewhere in our Milky Way galaxy.
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Nick – For your 30 min stack the length of the trails in your image is around 50 arcsec. The Hubble image that Denis linked shows a short (approx 4 arcsec) and very faint extension in PA 300 or so. I doubt that you are detecting the coma yet but your image is definitely of high quality.
The HST constraints on nucleus diameter are interesting. Details are in the ArXiv paper here: https://arxiv.org/pdf/2508.02934.
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